Is fat breathed out of our bodies?

Yes, you do burn off off fat when you lose weight.  But you also breathe out a lot of fat atoms when you exhale carbon dioxide.

That's the conclusion of a team of Australian scientists who calculated that when fat breaks down, chemical bonds are broken, which then releases heat and fuel to power muscles. But fat atoms stay in the body and have to be excreted by the lungs as carbon dioxide. The scientists referred to the lungs as the "primary excretory organ for weight loss."

Fat from food is stored in the body as a compound called triglyceride. When this compound is broken down, about a fifth of it forms water; the remaining four-fiths becomes carbon dioxide. The researchers estimate that the average person loses at least 200 grams of carbon every day with roughly a third of that loss occurring when we sleep.  But they point out that replacing one hour of rest with moderate intensity exercise, such as jogging, removes an additional 40 grams of carbon from the body.

So don't expect to lose much weight just by standing still and hyperventilating. The scientists note that exercise is necessary to begin breaking down fat into its components, including carbon dioxide.

The study was published in the Christmas edition of the British Medical Journal.

NEXT: Blood test can predict heart disease risk

Sourced from: BBC News, Fat 'breathed out' of body via lungs, say scientists